W.  L.  IB/oL/n 


The,  la.KOnom^  f{n<i  Morphology  Of  Some-  HeW„- 

r/i«s(oorwm«  With  Gemcolarhe.  ■ 


- 


\ 


* 


< 


\ 


THE  TAXONOMY  AND  MORPHOLOGY  OF  SOME 
HELMINTHOSPORIUMS  WITH  GEN- 
ICULATE CONIDIA 


BY 


WALTER  LEROY  BLAIN 
A.  B.  WABASH  COLLEGE 
1916 


THESIS 


Submitted  in  Partial  Fulfillment  of  the  Requirements  for  the 

Degree  of 


MASTER  OF  ARTS 
IN  BOTANY 


IN 


THE  GRADUATE  SCHOOL 

OF  THE 

UNIVERSITY  OF  ILLINOIS 


1921 


Digitized  by  the  Internet  Archive 
in  2015 


https://archive.org/details/taxonomymorpholoOOblai 


UNIVERSITY  OF  ILLINOIS 


THE  GRADUATE  SCHOOL 


May  5 191??: 


I HEREBY  RECOMMEND  THAT  THE  THESIS  PREPARED  UNDER  MY 


SUPERVISION  BY — Walter  Leroy  Blain 

entttt  f.d  The  Taxonomy  and  Morphology  of  some  Helmintho- 

sp oriuma  with  Geniculate  Conidla. 

BE  ACCEPTED  AS  FULFILLING  THIS  PART  OF  THE  REQUIREMENTS  FOR 
THE  DEGREE  OF Ma,s-te-r  of  Art-s 


In  ^Charge  of  Thesis 


Head  of  Department 


Recommendation  concurred  in* 


Committee 


on 


Final  Examination* 


*Required  for  doctor’s  degree  but  not  for  master’s 


) 


TABLE  OF  CONTENTS. 


Page 

I.  Introduction — 1 

II.  Key  to  Genera  Ordinarily  Confused 

with  Helmintho sporium  — 2 

III.  Accession  List,  — — — — 5 

IV.  Methods  of  Study — 6 

V.  Descriptions  of  Forms  Studied  — — — 8 

VI.  Variations -_12 

VII.  Conclusions  — - — — — — 13 

VIII.  Literature  Cited  — — .. — — 


. 
. 


; I 


-1- 


I.  Introduction. 

Those  species  of  the  genus  Helminthosporiura  character- 
ized by  conidia  of  from  3 to  5 cells  differ  in  respect  to  the 
shape  of  a centrally  located  cell.  In  some  of  these  species  the 
cell  referred  to  is  equilateral;  in  others  it  is  not  equilateral 
in  that  it  is  knee-form  or  geniculate.  These  conidia  are  further 
characterized  by  the  fact  that  the  terminal  cells  are  much  lighte 
in  color  than  the  intervening  cells, 

Glosexy  allied  to  the  species  of  Helminthosporium  which 
exhibit  these  conidial  characters  are  species  that  are  now  regard- 
ed, for  one  reason  or  another,  as  belonging  to  certain  other 
genera.  This  similarity  in  conidial  structure  suggests  that  they 
are  oogeneric  with  Helmihthosporium.  In  the  genera  Acrothecium 
and  Brachysporium,  in  particular,  species  with  conidia  of  the 
geniculate  type  have  been  described.  Saccardo  (1)  lists  11  genera 
namely,  Acrothecium,  Blastotrichum,  Brachysporium,  Cercospora, 
Cladosporiura,  Clasterosporium,  Monotosporium,  Mystrosporium , 
Napicladium,  Scolecotrichum,  and  Vermicularia,  which  he  says  are 
frequently  confused  with  Helminthosporium. 


. 


. 


' 


. - 


-3- 


II.  Key  to  Genera 

Ordinarily  Confused  with  Helminthosporium. 

The  general  conception  of  the  relation  of  these  genera 
as  described  by  Lindau  (2)  is  shown  in  the  following  key: 

1.  Spores  in  pycnidia 

Pycnidia  appendaged  or  hairy,  conidia  cylindric,  fusoid, 


and  irregular — • — - — Verraicularia 

!•  Spores  on  separate  conidiophores 

2,  Conidiophores  and  conidia  pale  — — (Mucedinaceae) 

Conidia  3 to  several-celled,  long  — (Phragmosporae) 

Fertile  hyphae  manifest  and  distinct  from  the 

conidia,  irregularly  branched  — - Blastotrichum 

2.  Conidiophores  dark,  conidia  usually  dark  - (Dematiaceae) 

3.  Conidia  one-celled,  short  — — - — - ( Amerosporae) 

Conidiophores  distinct  from  the  mycelium,  conidia 
not  in  chains,  borne  terminally  on  simple  free 

conidiophores  — ■ — — — — (Monotosporae) 

Conidia  dark  ■ — — — — — — — — Monotospora 

3.  Conidia  2-celled  — — — (Didymosporae) 


Conidiophores  distinctly  different  from  the  mycelium 
Conidia  not  in  chains,  terminal  or  lateral, 
conidiophores  unbranched,  short  — — Scolecotrichum 
Conidia  in  chains,  conidiophores  branched, 
long  - 


Cladosporium 


‘ 


. . . 


. 


-3- 

3.  Conidia  with  three  or  more  cells,  long  

(Phragmosporae) 

Conidiophores  very  short  or  little  different  from 
the  conidia;  conidia  dark,  ovoid  to  cylindric  to 
vermicular,  separate,  solitary  — — — Clasterosporium 
Conidiophores  distinctly  different  from  the 

conidia  — — - — Napicladium 

4.  Conidiophores  stiff 

5.  Conidia  terminal,  solitary 

6.  Smooth,  long  --- — Helminthosporium 

6.  Conidia  shorter  — — --  Brachysporium 
4.  Conidiophores  lax 

5.  Conidia  in  terminal  heads  - Acrothecium 
3.  Conidia  muriform,  spindle-shaped,  long  -(Dictysporae) 
Conidiophores  stiff,  distinctly  different  from  the 


conidia;  conidia  terminal,  dark  ——————  Mystrosporium 

3,  Conidia  thread-like  or  vermiform,  with  one  or  more 

cells,  dark  or  hyaline  — (Scolecosporae) 

. _ - — — — — - Cercospora 


Though  all  these  genera  may  in  certain  instances  be 
confounded  with  Helminthosporium,  the  Helminthosporiums  with 
geniculate  conidia  are  readily  distinguished,  e.  g. , from  Vermi- 
cularia  by  the  absence  of  a pycnidium;  from  Mystrosporium  by  the 


- 

- 


■ 


. 


-4- 


ab8ence  of  murifonn  conidia;  and  from  Cercospora  by  the  absence 
of  vermiform  or  filiform  conidia.  The  other  genera  listed  by 
Saccardo  as  being  confused  with  Helminthosporium,  differ  very 
little  from  each  other  with  respect  to  these  characters.  In  the 
latter  differentiation  is  based  upon  the  number  of  cells  in  the 
conidia  and  the  length  of  conidiophores.  Such  characters  are 
variable  and  often  lead  to  confusion. 

That  the  present  conceptions  of  generic  limitations 
do  not  agree,  is  brought  out  very  forcefully  by  the  incorrect 
placing  of  at  least  36  of  the  334  species  listed  by  Saccardo 
as  belonging  to  the  genus  Helminthosporium.  For  example,  the 
genus  Helminthosporium  is  defined  by  Saccardo  as  follows:  "Hyphae 
rigidulae,  subsimplices,  fuscae,  saepius  epixylae.  Conidia 
fusoidea,  vel  elonga-to-ciavata,  vel  cylindracea,  plurisepta, 
fusca,  rigida,  levia."  He  lists  one  species  with  no  septum,  one 
with  0 to  3,  three  with  1 to  3,  eight  with  -1  to  3,  three  with  3, 
eight  with  3 to  3,  and  two  with  1 to  4. 

The  geniculate  type  of  conidium  has  been  reported  in 
only  three  of  the  genera  listed  above,  namely,  Acrothecium,  Brachy- 
sponum,  and  Helminthosporium.  As  the  present  paper  is  concerned 
with  this  peculiar  conidial  type,  closer  attention  may  therefore 
be  given  to  the  differences  upon  which  the  separation  of  these 
genera  is  based.  Saccardo,  Lindau  (3)  and  Clements  (3)  state 
that  the  three  genera  are  very  similar  with  respect  to  this 


■ 

. 


■ 


■ 


..  .. 


character.  Acrothecium  is  characterized  by  acrogenous  conidia 
forming  a headj  while  Brachysporium  and  Helminthosporium  are 
characterized  by  having  the  conidia  borne  terminally  and  usually 
singly.  Helminthosporium  is  set  apart  from  the  former  genus 
through  having  longer  conidia. 

The  purpose  of  the  present  paper  is  to  make  a compara- 
tive study  of  all  the  available  forms  of  these  closely  allied 
genera  possessing  geniculate  conidia.  The  following  accession 
list  shows  the  forms  under  study,  which  will  hereafter  be  referred 
to  by  number,  and  indicates  also  their  origin  and  the  essential 
points  of  their  history. 

III.  Accession  List. 

The  forms  embraced  in  the  present  study  are  given  in 
the  following  accession  list: 

No.  35  was  isolated  from  the  Missouri  black  raspberry  by  Leva  B. 
Walker  of  the  University  of  Nebraska,  Lincoln,  Nebraska,  on  July 
4,  1919. 

No.  37  was  isolated  from  Sudan  Grass  (Andropogon  sp.),  grown  in 
a moist  chamber  by  the  writer  on  October  13,  1930. 

No.  28  was  isolated  from  Amber  Cane  (Andropogon  sorghum)  by  F.  L. 
Stevens  on  December  7,  1930. 

No.  29  was  isolated  from  a broken  corn  stalk  at  Fort  Branch, 
Indiana,  by  G.  N.  Hoffer  on  August  13,  1919. 


* 


-6- 


No.  30  was  isolated  from  brown,  water-soaked  lesions  on  the 
sheath  of  a corn  leaf  collected  at  Sullivan,  Indiana,  by  G.  N. 
Hoffer  on  August  12,  1919. 

No.  31  was  isolated  from  small,  brown,  regular  spots  on  corn 
leaves  from  Delphi,  Indiana,  by  G.  N.  Hoffer  in  August,  1919. 

No.  32  was  isolated  from  very  small,  yellow  spots  on  corn  leaves 
from  Battle  Ground,  Indiana,  by  G.  N.  Hoffer  on  August  7,  1919. 

The  writer  has  attempted  to  isolate  a large  number  of 
forms  from  as  many  diverse  hosts  as  possible.  The  seven  forms 
described  in  this  paper  have  all  been  isolated  from  some  member 
of  the  grass  family  (Gramineae) , with  the  exception  of  one  found 
on  the  Missouri  black  raspberry.  The  forms  isolated  from  grasses 
were  obtained  by  partially  disinfeoting  the  seeds  with  Javelle 
water,  in  order  to  lessen  the  amount  of  Mucor,  Altemaria,  and 
other  saprophytes.  The  seeds  were  then  placed  in  a sterile  moist 
chamber  to  germinate.  After  the  seeds  had  grown  for  about  three 
days,  those  infected  with  the  knee-formed  type  of  Helminthospor- 
ium  could  be  recognized  easily  by  their  general  appearance,  and 
these  seeds  were  removed  with  sterile  forceps  and  placed  on  corn- 
meal  agar. 


IV.  Methods  of  Study. 


In  order  to  simulate  the  conditions  in  which  the 


. 


. 


-7- 


fungus  grows  normally,  a standard  method  of  study  was  adopted. 

The  organism  was  planted  on  washed  agar,  nearly  devoid  of  organic 
material,  and  allowed  to  grow.  After  the  colony  had  reached  the 
size  of  a dime,  sterile  wheat  shoots,  about  two  inches  in  length, 
were  placed  on  the  agar.  The  sterile  shoots  were  obtained  by 
growing  aseptic  wheat  in  sterile  moist  chambers  until  the  shoot 
reached  a height  of  about  two  inches,  when  they  were  cut  off, 
placed  in  a vial  and  autoclaved.  The  cultures  were  kept  in  an 
incubator  at  a temperature  of  18  C.  to  30  C. 

In  measuring  the  conidia  a standard  method,  whereby 

0 

error  would  be  reduced  to  a negligible  minimum  and  the  unconcious 
selection  of  spores  would  be  eliminated,  was  adopted.  To  prevent 
the  conidia  from  floating  away  or  slipping  from  under  the  cover 
glass,  vaseline  was  used.  With  a dissecting  needle,  two  smears 
of  vaseline  were  placed  on  a glass  slide,  separated  from  each 
other  far  enough  so  that  the  smears  would  be  just  inside  the 
edges  of  the  cover  gla33.  With  a sterile  needle,  conidia  were 
placed  in  distilled  water  between  the  smears  of  vaseline  and 
covered  with  the  cover  glass.  A Leitz  Wetzlar  mechanical  stage 
was  used  and  only  conidia  which  were  in  a predetermined  position 
in  the  field  were  measured.  A Spencer  ocular  micrometer  with  a 
movable  scale  was  used  in  all  measurements. 


-8- 


V.  Descriptions  of  the  Forms  Studied. 

% 

In  studying  the  culture  characters,  such  as  color, 
zone  formation,  aerial  and  submerged  mycelium,  etc.,  of  these 
various  forms,  corn-meal  agar,  prepared  according  to  the  formula 
of  Shear  and  Stevens  (4) , was  used. 

The  plan  followed  in  presenting  the  data  is  that  of 
describing  one  organism,  No.  25,  and  then  considering  each  of 
the  remaining  organisms  as  to  how  it  differs  from  the  one  fully 
described.  Fungus  No.  25  shows  a very  faint  zonation.  The  colony 
when  three  or  four  days  old  has  a whitish  appearance,  but  it  turns 
to  grayish-black  as  it  matures.  The  submerged  mycelium  is  hyaline 
and  much  septate,  the  cells  varying  from  3.5  to  7.1  p.  in  width 
and  from  17.9  to  25  p.  in  length.  The  aerial  mycelium  is  of  a 
light  gray  color,  with  the  cells  ranging  from  3.5  to  7.1  p,  in 
width  and  from  14.2  to  30  u in  length.  For  the  sake  of  conven- 
ience in  describing  the  conidiophores , the  terms  stalk  and  sporo- 
genous  region  are  used.  The  former  refers  to  the  part  between 
the  mycelium  and  the  place  where  the  conidia  are  borne,  and  the 
latter  to  the  part  where  the  conidia  are  produced.  The  conidio- 
phores, arising  as  simple,  very  rarely  branched  outgrowths  or 
branches  of  the  mycelium,  are  variable  in  color  and  length.  The 
young  conidiophores  are  from  3.5  to  17  p.  long  and  3.5  p.  wide,  and 
they  lack  the  knee-formed  sporogenous  region  which  is  characteris- 


-9- 


tic  of  the  older  ones.  In  color  they  differ  but  very  little 
from  the  mycelium.  The  older  conidiophores  are  pale  straw  color, 
from  14.2  to  186  p.  in  length  and  from  3 to  6 p,  in  width.  The 
sporogenous  region  is  from  3 to  71  p.  in  length  and  from  3 to  6 p 
in  width,  while  the  stalk  is  from  11  to  165  \i  in  length  and  is 
approximately  3,5  |i  in  width.  The  stalk  and  sporogenous  region 
are  often  of  approximately  the  same  length,  and  as  a rule  each 
is  divided  into  five  or  more  cells.  The  sporogenous  region  pre- 
sents a very  crumpled  appearance  with  many  close  geniculat ions, 
and  is  of  a lighter  color  than  the  stalk  of  the  conidiophore. 

The  place  of  attachment  of  the  conidia  on  the  conidiophores  is 
easily  recognized  by  the  scars  on  the  sporogenous  region.  These 
scars  vary  from  one  to  twelve  or  fifteen  in  number,  depending 
upon  the  age  of  the  conidiophore.  At  first  glance  the  conidia 
appear  to  be  borne  in  a head,  but  upon  closer  examination  one 
can  see  that  when  the  first  conidium  is  formed  the  main  branch 
ceases  to  grow.  The  conidiophore,  therefore,  grows  out  laterally 
from  near  the  base  of  the  conidium  and  on  the  branch  a new  conid- 
ium is  formed.  This  process  may  be  repeated  many  times. 

A graph  representing  the  conidial  length  is  shown  in 
Plate  I.  The  modal  length  is  21.4  ijl,  with  few  conidia  of  shorter 
length  than  the  mode,  but  with  many  conidia  of  greater  length 
than  the  mode,  the  largest  measured  being  46.4  uu  The  width  of 
the  conidia  is  represented  in  the  polygon  in  Plate  II,  with  most 


■ 


. 


-10- 


of  the  conidia  between  7.1  and  10.7  n.  The  conidia,  as  shown 
in  Plate  III,  are  usually  three  or  four  septate.  The  apical 
end  of  the  conidium  is  obtuse  and  the  base  is  somewhat  acute. 

The  basal  cell  is  easily  identified  by  the  stipe  which  marks 
the  place  of  attachment  to  the  conidiophore.  The  walls  of  the 
conidia  are  very  brittle,  as  is  shown  by  the  fact  that  a very 
slight  tap  on  the  cover  glass  is  sufficient  to  crush  them, 
causing  the  contents  to  pass  out.  The  conidia  are  characterized 
by  their  knee-formed  appearance  or  geniculation.  This  genicula- 
tion,  which  is  due  to  a greater  growth  on  one  side  than  on  the 
other  side  of  the  conidium,  is  much  more  pronounced  in  some 
conidia  than  in  others.  In  a van  Tieghem  cell  the  conidia  ger- 
minate in  water  in  from  three  to  six  hours.  Each  terminal  cell 
of  the  conidia  sends  out  a germ  tube,  while  the  remaining  cells 
fail  to  show  this  phenomenon.  When  young,  the  conidia  are  green- 
ish-brown in  color  and  are  remarkably  uniform  in  this  respect. 

When  mature  they  become  darker,  and  then  the  end  cells  are  very 
much  lighter  in  color  than  the  intervening  cells. 

With  respect  to  colony  character,  Nos.  29  and  31  are 
very  similar  to  No.  25  in  color,  though  No.  29  is  perhaps  a little 
darker.  In  zonation  these  forms  also  agree  very  closely.  No.  27 
has  a very  definite  zonation  and  a grayish-brown  color.  No.  28 
has  a definite  zonation.  The  colony  is  of  an  olive-drab  color, 
and  the  mycelium  has  a ropy  appearance,  that  is,  twisted  into 


ijj  *»•?  ■'  ■ UUflE 

,^L.J 


-11- 

masses  at  the  ends.  No.  30  has  a fairly  abundant  growth  of 
mycelium,  dark  olive-drab  in  color.  The  zonation  is  scant,  but 
differs  from  the  other  races  in  regard  to  the  growth  of  mycelium, 
which  will  be  discussed  later.  No.  32  is  dark  olive-drab  in 
color,  with  marked  zonation,  and  a rather  large  growth  of  aerial 
mycelium.  This  last  character  is  not  very  marked  in  the  other 
forms,  although  they  do  exhibit  it  to  some  extent.  The  submerged 
and  aerial  mycelium  are  alike  in  all  of  the  forms.  No.  27  differs 
from  the  other  forms  in  conidiophore  character,  this  being 
branched,  while  in  the  other  forms  it  is  simple.  No  difference 
in  character  of  conidiophores  or  the  place  of  attachment  was 
noticed.  The  relation  of  the  various  forms  as  regards  conidia, 
conidiophores,  and  cultural  characters  is  shown  in  Tables  1 and  3. 

From  the  accompanying  curves,  Plate  I,  it  may  be  seen 
that  there  is  some  difference  between  the  various  forms  in  conid- 
ial  length.  Organism  No.  25  is  set  apart  somewhat  from  the  rest 
by  the  modal  length  of  its  conidia.  The  conidia  of  No.  37  have 
a modal  length  of  36  p;  those  of  No.  28,  the  largest  of  those 
studied,  a modal  length  of  32  p.  Nos.  39,  30,  and  31  all  fall 
virtually  in  the  same  class,  with  a modal  length  of  25  p.  No.  32 
is  of  a somewhat  different  type,  as  is  shown  by  the  fact  that 
as  many  conidia  measure  26  and  29.5  p as  measure  33  p,  which  is 
the  modal  length.  From  the  study  of  the  graphs  showing  conidial 
length,  Plate  I,  it  appears  probable  that  at  least  three,  and 


' 


-13- 


perhaps  four,  different  forms  or  elementary  species  are  repre- 
sented. Further  investigation  is  necessary,  however,  before 
this  conclusion  may  be  drawn. 

Plate  II  shows  the  width  of  the  conidia  to  range  from 
7.14  to  14.3  |jl,  with  the  majority  measuring  10.7  y.  From  the 
polygons,  Plate  III,  showing  septation,  it  can  be  seen  that  the 
septa  vary  from  one  to  four,  but  the  most  of  the  conidia  are 
four-septate.  Because  of  the  similarity  in  conidial  width  and 
septation,  as  is  shown  in  Plates  II  and  III,  these  characters 
do  not  differentiate  one  form  from  another.  The  apices  and  base 
of  the  conidia  in  the  various  forms  were  alike,  as  far  as  deter- 
mined, so  none  of  these  forms  could  be  set  apart  from  others  by 
these  characters.  The  color  of  the  conidia  in  all  of  the  forms 
is  the  same  when  the  conidia  are  mature. 

VI.  Variations. 

In  studying  the  various  forms  as  they  grew  on  corn- 
meal  agar.  No.  30  exhibited  certain  characters  which  were  dis- 
tinctly different  from  those  of  the  other  cultures.  In  No.  30 
certain  sectors  of  the  colonies  were  very  much  darker  than  the 
rest  of  the  colony.  In  order  to  ascertain  whether  these  darker 
sectors  were  of  permanent  character,  several  experiments  were 
made.  Transfers  from  many  of  the  darkened  sectors,  as  well  as 


' ■ 


-13- 


from  the  rest  of  the  colony,  were  made  and  the  results  noted. 

The  transfers  from  the  dark  areas  always  failed  to  retain  this 
character,  which  was  so  evident  when  they  were  planted  on  the 
culture  medium,  and  reverted  to  the  color  of  the  original  colony. 
Transfers  made  from  the  original  colony  continued  to  produce 
occasional  dark  areas,  but  when  transfers  were  made  from  these 
dark  sectors  the  resulting  colony  showed  a reversion  to  the 
characters  of  the  original  mycelium.  These  experiments  were 
repeated  many  times,  and  in  every  case  the  sectors  fluctuated 
back  and  forth  with  respect  to  this  character  and  gave  evidence 
of  permanency. 

VII.  Conclusions. 

From  the  descriptions  of  the  forms  listed  above  it 
is  plainly  evident  that  only  races,  varieties  or  elementary  species 
of  the  genus  Helminthosporium  are  enumerated  in  this  paper.  Since 
the  conidia  are  borne  one  above  the  other  in  a sympodial  manner, 
it  is  certain  that  Acrothecium  and  Brachysporium  can  be  dismissed 
as  being  genera  in  which  the  described  forms  may  be  placed.  In 
the  genus  Acrothecium  the  conidia  are  borne  in  a head  at  the  end 
of  the  conidiophore , and  this  character  alone  throws  this  genus 
out  of  consideration.  The  genus  Brachysporium,  according  to 
Lindau  (2),  is  characterized  by  having  conidia  that  are  not  more 
than  twice  as  long  as  wide.  From  the  graphs,  Plate  I,  and  poly- 


s 

■ 


I 


-14- 


gons,  Plates  II  and  III,  which  show  very  conclusively  that  the 
conidia  in  the  forms  studied  do  not  fall  into  this  category,  it 
is  evident  that  this  genus  can  also  be  dismissed  from  considera- 
tion. With  these  two  genera  eliminated  Helrainthosporium  only 
remains.  Stevens  (5),  in  mentioning  the  last  four  forms  studied, 
says  that  they  agree  very  closely  with  each  other  and  according 
to  spore  measurement  approach  H.  inaequale  Shear,  H.  tritici 
P.  Henn. , and  H.  geniculatum  T.  & E.  Further  study  of  these 
forms  is  necessary  before  the  status  of  these  species  may  be 


known. 


-15- 


VIII.  Literature  Cited. 

(1)  Saccardo,  P.  A.  Sylloge  Fungorum  Omnium  Hucuaque 

Cognitorum.  18:828. Padua.  1910. 

(2)  Lindau,  G.  in  Engler  and  Prantl,  Die  Naturlichen 

Pflanzenf amilien.  1:  Leipzig.  1900. 

(3)  Clements,  F.  E.  The  Genera  of  Fungi.  Minneapolis. 

1909. 

(4)  Shear,  C.  L. , and  Stevens,  N.  E.  Cultural  characters 

of  the  chestnut  blight  fungus.  Bur.  PI.  Ind. 
Circ.  131.  1913. 

(5)  Stevens,  F.  L.  The  Helminthosporium  foot-rot  of 

wheat,  with  observations  on  the  morphology  of 
the  genus  Helminthosporium  and  of  the  occurrence 
of  saltation  in  the  genus.  To  be  published  in 
the  111.  Nat.  Hist.  Sur.  Bull. 


-16- 


Table  1. 

Conidia 


No.  of 

fungus  Length  in  microns  Breadth  in  microns 


Mode 

Mini- 

Maxi- 

Mode 

Mini- 

Maxi- 

mum 

mum 

mum 

mum 

35 

21.42 

14.28 

42.84 

7.14 

7.14 

14.28 

27 

28.56 

10.71 

39.27 

110.71 

7.14 

14.38 

28 

35.7 

17.85 

42.84 

10.71 

7.14 

14.28 

39 

35.99 

14.28 

39.27 

10.71 

7.14 

10.71 

30 

25.99 

18.85 

46.41 

10.71 

7.14 

14.28 

31 

25.  99 

10.71 

46.41 

10.71 

7.14 

14.28 

32 

32.13 

14.38 

43.84 

10.71 

7.14 

14.28 

Septa 


1 to  4 usu- 
ally four 

3 to  4 usu- 
ally four 

3 to  4 usu- 
ally four 

3 to  4 usu- 
ally four 

1 to  4 usu- 
ally four 

3 to  4 usu- 
ally four 

1 to  4 usu- 
ally four 


. 


-17- 


i 

Table  2. 


Conidiophores 

No.  of 


ngus 

Stalk 

Sporogenous 

region 

Length 

Length 

Nc 

i.  of 

in  |jl 

in  |jl 

soars 

25 

11  to 

3.57 

1 

to  12 

165 

to  46 

OI 

■ 15 

27 

7.14  to 

7.14 

1 

to  13 

150 

to  42.8 

28 

7.14  to 

7.14 

1 

to  12 

171 

to  71.4 

29 

10. 71 to 

7.14 

1 

to  11 

111 

to  42 • 8 

30 

7.14  to 

7.14 

1 

to  10 

150.6 

to  54 

31 

10. 71to 

3.57 

1 

to  10 

164 

to  46.4 

32 

5.36  to 

7.14 

1 

to  12 

157 

to  42.8 

Culture  Characters 


Zona- 

tion 

Aerial 

mycel- 

ium 

Color  of 
colony 

Density 

Very 

scant 

Gray 

Grayish- 

black 

Sparse 

Defin- 

ite 

Gray 

Grayish- 

brown 

Medium 

Defin- 

ite 

Gray 

Olive- 

drab 

Medium 

Scant 

Gray 

Light 

grayish- 

brown 

Medium 

Medium 

Gray 

Olive- 

drab 

Medium 

Scant 

Gray 

Grayish- 

brown 

Medium 

Defin- 

ite 

Gray 

Dark 

olive- 

drab 

Medium 

-18“ 


Plate  I.  Graphs  showing  lengths  of  oonidia  in  Nos 
25,  27,  28,  29,  30,  31,  32.  Each  space  on  the  ab- 
scissa equals  3.57  p.. 


-19- 


Plate  II.  Polygons  showing  widths  of  conidia  in  Nos. 

25,  27,  28,  29,  30,  31,  32.  Each  space  on  the  abscissa 
equals  3.57  u. 


Plate  III.  Polygons  showing  septation  in  conidia  in 

Nos.  25,  27,  28,  29,  30,  31,  32.  Each  space  on  the 
abscissa  represents  one  septum. 


-20- 


4P 

r/>  ctT 


% 


ry 

Plate  IV.  Showing  conidia  of  No.  25. 


Plate  V.  Showing  conidia  of  No.  30. 


